The Variable Line Width of Achernar

TL;DR

This study confirms that Achernar's photospheric line width varies with emission activity, suggesting a possible link to re-accretion processes, supported by new and archival spectroscopic data.

Contribution

It provides new observational evidence of variable line width in Achernar and compares it with similar phenomena in other stars, exploring the underlying mechanisms.

Findings

Confirmed $v \, \sin i$ variation correlates with emission activity

Leans towards re-accretion as the cause of line width changes

Includes analysis of similar effects in 66 Oph and π Aqr

Abstract

Spectroscopic observations of Achernar over the past decades, have shown the photospheric line width, as measured by the rotational parameter $v \sin i$, to vary in correlation with the emission activity. Here we present new observations, covering the most recent activity phase, and further archival data collected from the archives. The $v \sin i$ variation is confirmed. On the basis of the available data it cannot be decided with certainty whether the increased line width precedes the emission activity, i.e. is a signature of the ejection mechanism, or postdates is, which would make it a signature of re-accretion of some of the disk-material. However, the observed evidence leans towards the re-accretion hypothesis. Two further stars showing the effect of variable line width in correlation with emission activity, namely 66 Oph and $\pi$ Aqr, are presented as well.